Internal combustion engine

Abstract

To provide an internal combustion engine that has high cost effectiveness and can easily detect leakage in a valve of a fuel supply system to avoid damage in a wide range and a risk of potential safety.SOLUTION: An internal combustion engine for vessel propulsion includes at least one cylinder and a fuel supply system. The fuel supply system includes: a first cylinder fuel supply passage including a first main valve and a first auxiliary valve disposed upstream of the first main valve; and a second cylinder fuel supply passage including a second main valve and a second auxiliary valve disposed upstream of the second main valve. A first pressure sensor providing a first pressure signal is disposed between the first main valve and the first auxiliary valve, and a second pressure sensor providing a second pressure signal is disposed between the second main valve and the second auxiliary valve. The internal combustion engine further includes a comparison unit that compares the first pressure signal with the second pressure signal in order to detect non-correspondence between the first and second pressure signals. This invention also relates to a leakage detection method for detecting leakage in a valve of the fuel supply system and a computer program product.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an internal combustion engine for the propulsion of a ship having at least one cylinder. The present invention also relates to a leakage detection method for detecting leakage in a valve in a fuel supply system and to a computer program product.

Background Art

[0002] When designing ships such as container ships and tankers, the main focus is on operating in a cost - efficient manner while preventing on - board safety and environmental damage. To operate in a safe and cost - efficient manner, it is important to detect engine component malfunctions before the components become defective and need to be replaced and before the malfunctions affect other engine components.

[0003] Small leaks in fluid passages, valves, etc. are difficult to detect but important because they are small, and because the damage is also very small, only small - scale repairs or replacements such as just the leaking valve are required, and there is no need to replace related components. However, if the leak is not detected while it is small, the repair will be much more extensive and costly, and the ship may even be prevented from operating while the repair is being carried out.

Summary of the Invention

Problems to be Solved by the Invention

[0004] It is an object of the present invention to overcome all or part of the above - mentioned disadvantages and drawbacks of the prior art. More specifically, it is an object to provide an improved internal combustion engine that can detect valve leakage in a fuel supply system by a simple method while still being cost - effective and avoiding extensive damage and potential safety hazards.

Means for Solving the Problems

[0005] The above object, together with numerous other objects, advantages, and features that will become apparent from the following description, is an internal combustion engine for ship propulsion, the internal combustion engine having at least one cylinder, - a fuel supply system, - a first cylinder fuel supply passage including a first main valve and a first sub-valve disposed upstream of the first main valve, - a second cylinder fuel supply passage including a second main valve and a second sub-valve disposed upstream of the second main valve and comprising a fuel supply system, a first pressure sensor that provides a first pressure signal is disposed between the first main valve and the first sub-valve, and a second pressure sensor that provides a second pressure signal is disposed between the second main valve and the second sub-valve, The internal combustion engine further comprises a comparison unit that compares the first pressure signal with the second pressure signal to detect a discrepancy between the first pressure signal and the second pressure signal, and is achieved by the solution according to the present invention by the internal combustion engine.

[0006] Also, the at least one cylinder can be a first cylinder, and the internal combustion engine can further comprise a second cylinder.

[0007] In addition, the first cylinder fuel supply passage supplies fuel to one of the first and second cylinders, and the second cylinder fuel supply passage supplies fuel to one of the first and second cylinders.

[0008] In other internal combustion engines for ship propulsion, the internal combustion engine can have at least a first cylinder and a second cylinder, - a fuel supply system, - a first cylinder fuel supply passage for supplying fuel to one of the first and second cylinders, comprising a first main valve and a first sub-valve disposed upstream of the first main valve, - a second cylinder fuel supply passage for supplying fuel to one of the first and second cylinders, comprising a second main valve and a second sub-valve disposed upstream of the second main valve comprising a fuel supply system, A first pressure sensor that provides a first pressure signal is disposed between a first main valve and a first sub-valve, and a second pressure sensor that provides a second pressure signal is disposed between a second main valve and a second sub-valve. The internal combustion engine further comprises a comparison unit that compares the first pressure signal with the second pressure signal to detect a discrepancy between the first pressure signal and the second pressure signal.

[0009] When the internal combustion engine is operating at low load and / or low pressure, the pressure in the fuel supply system does not increase to the same extent, such as 300 bar, when the valve is closed as when the engine is operating at high load or high pressure. Therefore, more conventional methods of leak detection do not function sufficiently effectively. However, by measuring and comparing the pressure or its representation between the main valve and the sub-valve in both the first cylinder fuel supply passage and the second cylinder fuel supply passage, ambient factors such as low pressure and low load equally affect the pressure in each of the first cylinder fuel supply passage and the second cylinder fuel supply passage, and thus, it is not necessary to be so high to detect even a small leak where the pressure increase is small, so a small leak or malfunction can be detected.

[0010] By measuring and comparing the pressure or its representation between the main valve and the sub-valve in both the first cylinder fuel supply passage and the second cylinder fuel supply passage, the pressure signals can be compared. Therefore, even if the pressure signal changes, even if the supply pressure changes, or even if other factors around the fuel supply system change, the mutual relationship between those pressure signals will be quite stable, so a leak or malfunction can still be detected, although it is very small.

[0011] In that method, an improved internal combustion engine is obtained that can detect valve leakage or malfunction in a fuel supply system by a simple method. Such detection can avoid extensive damage and safety hazards, which means that the internal combustion engine is more cost-effective because the repair or replacement of a leaking or malfunctioning valve can be carried out before major damage occurs.

[0012] In known internal combustion engines, detection of valve leakage in the fuel supply passage that supplies fuel to the cylinders is carried out using several tests such as a volume test, a drip test, a curve fit test, a fluctuation test, and a maximum pressure test so that leakage or malfunction can be detected at an early stage. In particular, the curve fit test has been found to be inappropriate for engines operating at low pressure and low load. The present invention requires only one test.

[0013] Also, the first cylinder fuel supply passage can be in fluid connection with the first cylinder, and the second cylinder fuel supply passage can be in fluid connection with the first cylinder or the second cylinder.

[0014] Moreover, the first cylinder fuel supply passage can be in fluid connection with the first cylinder for fuel injection into the first cylinder, and the second cylinder fuel supply passage can be in fluid connection with the first cylinder for fuel injection into the first cylinder, or the second cylinder fuel supply passage can be in fluid connection with the second cylinder for fuel injection into the second cylinder.

[0015] Furthermore, the fuel supply system can include a main supply passage that is in fluid connection with the first cylinder fuel supply passage and the second cylinder fuel supply passage.

[0016] In addition, the main supply passage is arranged upstream of the first cylinder fuel supply passage and the second cylinder fuel supply passage.

[0017] Furthermore, the fuel supply system can include a pump, and the main supply passage can be fluidly connected to the pump to feed fuel to both the first cylinder fuel supply passage and the second cylinder fuel supply passage.

[0018] In addition, the fuel supply system can include a pressure control valve, and the main supply passage can be fluidly connected to the pressure control valve to control the fuel to both the first cylinder fuel supply passage and the second cylinder fuel supply passage.

[0019] Also, the first pressure sensor can measure a real-time and / or continuous first pressure signal, and the second pressure sensor can measure a real-time and / or continuous second pressure signal.

[0020] Moreover, the fuel can be propane, butane, methanol, methane, ethanol, ethene, ethane, ammonia, propylene, butylene, isobutane, n-butane, hydrogen, kerosene, nitromethane, liquefied petroleum gas, bioethanol, or biodiesel.

[0021] Furthermore, the fuel can be the only fuel supplied to at least one cylinder.

[0022] In addition, the fuel can be a secondary fuel, and the primary fuel can be diesel, gasoline, or petroleum.

[0023] Moreover, the primary fuel can have at least 0.05% sulfur content.

[0024] Furthermore, the fuel can be liquid or gas.

[0025] Also, the main valve can have an opening time period shorter than that of the sub-valve.

[0026] Moreover, the sub-valve can open before the main valve opens.

[0027] By using the measurements and comparisons of the present invention, in particular, leaks or malfunctions in the pilot valve can be monitored and detected, which is very difficult in known systems where a curve fitting test is performed. When using a curve fitting test, the measured pressure is usually compared with a reference curve, but external factors such as operation at low load or low pressure will affect the result. Therefore, the intervals at which the measured pressure differs from the reference curve need to be very wide in order to also conform to engine operation at low load and low pressure. When the intervals need to be wide so that the engine is not inadvertently stopped, small leaks are not detected. Leaks in the pilot valve, also called the window valve, can pose a potential safety hazard, and therefore it is important to detect such leaks at an early stage.

[0028] In addition, the pilot valve may open while the main valve is closed.

[0029] Furthermore, the pilot valve may be closed while the main valve is closed.

[0030] Also, the main valve may open and / or close while the pilot valve is open.

[0031] Moreover, the first pressure signal may form a first pattern, the second pressure signal may form a second pattern, and the comparison unit can compare the first pattern with the second pattern to detect a correlation and verify whether the correlation is within a predetermined interval.

[0032] "Correlation" means any statistical relationship such as the statistical variance between two sets of pressure signal data, that is, any type of relationship that refers to the degree to which pairs of variables are made to have a linear relationship.

[0033] Furthermore, the comparison unit can be a central processing unit (CPU), a control unit, an integrated circuit such as a microchip or chip, a comparative unit, or a comparator based on hardware or software.

[0034] In addition, the comparison unit may include pattern recognition software.

[0035] Moreover, the internal combustion engine may also include a third cylinder and a fourth cylinder into which fuel is respectively fed from two fuel supply passages each having a pressure sensor, a sub-valve, and a main valve.

[0036] In addition, the internal combustion engine may also include at least six cylinders.

[0037] Furthermore, the first pressure signal may have a predetermined number of data points within a predetermined time period.

[0038] In addition, the second pressure signal may have a predetermined number of data points within a predetermined time period.

[0039] Furthermore, the predetermined time period may be from a certain operating position of one of the valves until the same operating position is performed again.

[0040] Also, the predetermined time period may be from closing the sub-valve until closing the sub-valve next time.

[0041] Moreover, the combustion engine system may further include a turbocharger disposed downstream of the internal combustion engine.

[0042] Furthermore, the turbocharger may include a turbine and a compressor.

[0043] In addition, the present invention is a method for detecting leakage or malfunction of a valve in a fuel supply system for supplying fuel to at least one cylinder of an internal combustion engine, - In a first cylinder fuel supply passage of the fuel supply system, measuring a first pressure signal in a first time period by a first pressure sensor between a first main valve and a first sub-valve; - In the second cylinder fuel supply passage of the fuel supply system, measuring a second pressure signal by a second pressure sensor between a second main valve and a second sub-valve in a first time period or a second time period; - Comparing a first pressure signal with a second pressure signal to detect a leak in one of the valves or a malfunction of one of the valves; relates to a method for detecting a leak or a malfunction, including the above steps.

[0044] Furthermore, the present invention relates to a computer program product comprising a computer-readable medium holding computer program code means, which, when loaded, causes the computer program product to cause a computer to execute the method for detecting a leak or a malfunction.

[0045] Furthermore, the internal combustion engine may be a large two-stroke internal combustion engine.

[0046] In addition, the internal combustion engine may be a crosshead-type large two-stroke internal combustion engine with a turbocharger.

[0047] Furthermore, the internal combustion engine may be a two-stroke or four-stroke internal combustion engine.

[0048] The present invention and its advantages will be described in more detail below with reference to the accompanying schematic drawings showing some non-limiting embodiments for illustrative purposes.

Brief Description of the Drawings

[0049]

Figure 1

Figure 2

Figure 3

Figure 4

Best Mode for Carrying Out the Invention

[0050] All the figures are schematic and not necessarily to the same scale, showing only the parts necessary to clarify the present invention, with other parts omitted or merely suggested.

[0051] FIG. 1 is a schematic view of a fuel supply system 4 for an internal combustion engine 1 for the propulsion of a ship such as a container ship or a tanker. The internal combustion engine 1 can also be a stationary engine. Thus, the internal combustion engine 1 can be a two-stroke or four-stroke internal combustion engine 1. The internal combustion engine 1 includes a first cylinder 2 and a fuel supply system 4. The fuel supply system 4 includes a first cylinder fuel supply passage 5, 5a for supplying fuel to the first cylinder 2 and a second cylinder fuel supply passage 5, 5b for supplying fuel to the first cylinder 2. Thus, the first cylinder fuel supply passage 5, 5a is in fluid connection with the first cylinder 2 for injection of fuel into the first cylinder 2, and the second cylinder fuel supply passage 5, 5b is in fluid connection with the same first cylinder 2 for injection of fuel into the first cylinder 2 at different positions along the periphery of the first cylinder 2. The first cylinder fuel supply passage 5, 5a includes a first main valve 6, 6a and a first sub-valve 7, 7a arranged upstream of the first main valve 6, 6a. The second cylinder fuel supply passage 5, 5b includes a second main valve 6, 6b and a second sub-valve 7, 7b arranged upstream of the second main valve 6, 6b. Further, the fuel supply system 4 includes a first pressure sensor 8, 8a for providing a first pressure signal 9, 9a, and the first pressure sensor 8, 8a is arranged to measure the pressure between the first main valve 6, 6a and the first sub-valve 7, 7a. Also, the fuel supply system 4 includes a second pressure sensor 8, 8b for providing a second pressure signal 9, 9b and arranged to measure the pressure between the second main valve 6, 6b and the second sub-valve 7, 7b. The internal combustion engine 1 further includes a comparison unit 10 for comparing the first pressure signal 9, 9a and the second pressure signal 9, 9b to detect a discrepancy therebetween, and the discrepancy indicates a leak in one of the valves 6, 6a, 6b, 7, 7a, 7b. The comparison unit 10 receives the first pressure signal 9, 9a from the first pressure sensor 8, 8a and the second pressure signal 9, 9b from the second pressure sensor 8, 8b, as shown by the dotted line in FIG. 1.

[0052] Small leaks in the main valves 6, 6a, 6b or the auxiliary valves 7, 7a, 7b, or malfunctions of the main valves 6, 6a, 6b or the auxiliary valves 7, 7a, 7b are difficult to detect but important because the leaks are small, and only minor repairs or replacements of the leaking valves are required because the damage is also very small. Furthermore, leaks in the auxiliary valves 7, 7a, 7b, or malfunctions of the auxiliary valves 7, 7a, 7b can pose a potential safety hazard. However, if the leaks or malfunctions are not detected while they are small, the repairs will be much more extensive and costly, and the ship may even be prevented from operating while the repairs are being carried out.

[0053] When the internal combustion engine 1 operates at low load and / or low pressure, the pressure in the fuel supply system 4 does not increase to the same extent as when the engine operates at high load or high pressure, such as 300 bar, when the valves 6, 7 are closed. Therefore, more conventional methods of leak detection do not function effectively enough.

[0054] In known internal combustion engines, leak detection of valves in the fuel supply passages that supply fuel to the cylinders is carried out using several tests, such as volume tests, drip tests, curve fit tests, fluctuation tests, and maximum pressure tests, so that leaks or malfunctions can be detected at an early stage. In particular, the curve fit test has been found to be inappropriate for engines operating at low pressure and low load.

[0055] However, by measuring and comparing the pressure or its representation between the main valve 6 and the auxiliary valve 7 in both the first cylinder fuel supply passages 5, 5a and the second cylinder fuel supply passages 5, 5b, ambient factors such as low load and low pressure affect the pressure in each of the first cylinder fuel supply passages 5, 5a and the second cylinder fuel supply passages 5, 5b equally, so that it is not necessary to increase the pressure so high to detect small leaks or any malfunctions, and small leaks or malfunctions can be detected.

[0056] In both the first cylinder fuel supply passages 5, 5a and the second cylinder fuel supply passages 5, 5b, by measuring the pressure or its representation between the main valves 6, 6a, 6b and the sub - valves 7, 7a, 7b, the pressure signals can be compared. Therefore, even when the pressure signals 9a, 9b change, whether the supply pressure changes, or other factors around the fuel supply system 4 change, the correlation between these pressure signals will be quite stable. Thus, even though it is very small, leaks or malfunctions can be detected. In that way, an improved internal combustion engine 1 can be obtained in which leaks or malfunctions of the valves 6, 7 in the fuel supply system 4 can be detected by a simple method. By such detection, extensive damage and safety hazards can be avoided, which means that the internal combustion engine 1 is more cost - effective because repairs or replacements of leaking or malfunctioning valves 6, 7 can be carried out before major damage occurs. Furthermore, the present invention requires only one test.

[0057] The main valves 6, 6a, 6b have an opening time period shorter than that of the sub - valves 7, 7a, 7b. The sub - valves 7, 7a, 7b open before the main valves 6, 6a, 6b open. Therefore, the sub - valves 7, 7a, 7b also provide a window for fluid communication to the main valves 6, 6a, 6b and are thus called window valves. Accordingly, the sub - valves 7, 7a, 7b open while the main valves 6, 6a, 6b are closed, and the sub - valves 7, 7a, 7b close while the main valves 6, 6a, 6b are closed. The main valves 6, 6a, 6b open and / or close while the sub - valves 7, 7a, 7b are open.

[0058] The first pressure sensors 8, 8a measure real - time and / or continuous first pressure signals 9, 9a, and the second pressure sensors 8, 8b measure real - time and / or continuous second pressure signals 9, 9b. In this way, leaks or malfunctions can be detected at any given time during the continuous opening and closing of the valves 6, 6a, 6b, 7, 7a, 7b because the pressure signals 9, 9a, 9b can be compared during that continuous period, even though it is very small.

[0059] In FIG. 2, the internal combustion engine 1 includes a first cylinder 2 and a second cylinder 3. The fuel supply system 4 includes a first cylinder fuel supply passage 5, 5a for supplying fuel to the first cylinder 2 and a second cylinder fuel supply passage 5, 5b for supplying fuel to the second cylinder 3. The first cylinder fuel supply passage 5, 5a includes first main valves 6, 6a, first pressure sensors 8, 8a, and first sub-valves 7, 7a, and the second cylinder fuel supply passage 5, 5b includes second main valves 6, 6b, second pressure sensors 8, 8b, and second sub-valves 7, 7b. The first cylinder fuel supply passage 5, 5a is in fluid connection with the first cylinder 2 for injection of fuel into the first cylinder 2, and the second cylinder fuel supply passage 5, 5b is in fluid connection with the second cylinder 3 for injection of fuel into the second cylinder 3. In FIG. 2, the comparison unit 10 compares the first pressure signals 9, 9a of the first pressure sensors 8, 8a and the second pressure signals 9, 9b of the second pressure sensors 8, 8b to detect a discrepancy between the first pressure signal 9, 9a and the second pressure signal 9, 9b. The first pressure signal 9, 9a corresponds to the pressure measured in the first cylinder fuel supply passage 5, 5a that supplies fuel to the first cylinder 2, and the second pressure signal 9, 9b corresponds to the pressure measured in the second cylinder fuel supply passage 5, 5b that supplies fuel to the second cylinder 3. Since fuel is injected into the first cylinder 2 before being injected into the second cylinder 3, the peak of the first pressure signal 9, 9a is temporally shifted with respect to the peak of the second pressure signal 9, 9b.

[0060] In FIGS. 1 to 3, the fuel supply system 4 further includes a main supply passage 12 that is fluidly connected to the first cylinder fuel supply passages 5, 5a and the second cylinder fuel supply passages 5, 5b to supply fuel from the pump 11. Accordingly, the main supply passage 12 is arranged upstream of the first cylinder fuel supply passages 5, 5a and the second cylinder fuel supply passages 5, 5b. The pressure of the fuel entering the first cylinder fuel supply passages 5, 5a may vary slightly from the pressure of the fuel entering the second cylinder fuel supply passages 5, 5b, but the correlation between the first pressure signals 9, 9a and the second pressure signals 9, 9b is the same as when the differences in pressure are substantially the same. Comparing the first pressure signals 9, 9a and the second pressure signals 9, 9b still provides an early warning of a leak in one of the valves 6, 6a, 6b, 7, 7a, 7b or a malfunction of one of the valves 6, 6a, 6b, 7, 7a, 7b, and thus the detection of the leak or malfunction is independent of such pressure changes in the main supply passage 12.

[0061] The internal combustion engine 1 of FIG. 3 includes four cylinders, namely, a first cylinder 2, a second cylinder 3, a third cylinder 14, and a fourth cylinder 15. Both the third cylinder 14 and the fourth cylinder 15 are supplied with fuel from two fuel supply passages 5, 5a, 5b via a first portion 12a of the main supply passage 12 and a second portion 12b of the main supply passage 12. Each of the two fuel supply passages 5, 5a, 5b has a pressure sensor 8, a sub-valve 7, and a main valve 6. The fuel supply system 4 includes a pump 11 that supplies fuel to all four cylinders 2, 3, 14, 15 through the fuel supply passages 5, 5a, 5b.

[0062] As can be seen in Fig. 4, the first pressure signals 9, 9a form the first pattern P1, and the second pressure signals 9, 9b form the second pattern P2. Comparing the first pattern P1 with the second pattern P2 results in a correlation. The comparison unit 10 compares the first pattern P1 with the second pattern P2 to detect the correlation. When the correlation is within a predetermined interval, the valves 6, 6a, 6b, 7, 7a, 7b operate as planned. However, when the correlation is outside the predetermined interval, there may be a leak in one of the valves 6, 6a, 6b, 7, 7a, 7b, or there may be a malfunction in one of the valves 6, 6a, 6b, 7, 7a, 7b. In Fig. 4, the correlation is a smaller value in the second pressure signals 9, 9b. When the first pressure signals 9, 9a and the second pressure signals 9, 9b are continuously measured and compared, the patterns P1, P2 are the same, and the correlation is the same as long as the valves 6, 6a, 6b, 7, 7a, 7b operate as planned without leaks or malfunctions as shown in Fig. 4. If one of the first main valves 6, 6a or the first sub-valves 7, 7a does not operate according to the plan, the first pressure signals 9, 9a will change the first pattern P1, and the correlation will be outside the predetermined interval. Since the first pattern P1 may change due to pressure fluctuations somewhere in the fuel supply system 4, such changes will also affect the second pattern P2. When comparing the first pressure signals 9, 9a and the second pressure signals 9, 9b, if the change is due to other changes somewhere in the fuel supply system 4 rather than a malfunction in one of the main valves 6, 6a, 6b or the sub-valves 7, 7a, 7b, the correlation will be the same and within the predetermined interval. Therefore, when continuously comparing the first measured pressure and the second pressure, that is, when comparing the first pressure signals 9, 9a and the second pressure signals 9, 9b, other system changes are smoothed out, so the predetermined interval of the correlation can be set very narrow. By comparing the first pressure signals 9, 9a and the second pressure signals 9, 9b, small changes due to leaks in the main valves 6, 6a, 6b or the sub-valves 7, 7a, 7b, or malfunctions in the main valves 6, 6a, 6b or the sub-valves 7, 7a, 7b can be detected early.When the first pressure signals of types 9 and 9a are compared with other pressure signals, system changes may affect only one of the pressure signals. Therefore, the correlation interval needs to be set quite wide because the operation would stop too frequently. As a result, small leaks or malfunctions will not be detected as early as when comparing the first pressure signals 9, 9a with the second pressure signals 9, 9b.

[0063] In FIG. 4, when the first pressure signals 9, 9a are measured continuously in real time, they have a predetermined number of data points over a predetermined time period. The second pressure signals 9, 9b are illustrated by dotted lines, but also have a predetermined number of data points over a predetermined time period when measured continuously in real time. The predetermined time period can be from when the sub-valves 7, 7a, 7b close (illustrated by arrow C2 in FIG. 4) to when they close next, or from a certain operating position to any other period until the same operating position occurs again, that is, it can be continuous and include one or all of the operating positions of the valves 6, 6a, 6b, 7, 7a, 7b where both the main valves 6, 6a, 6b open and close and both the sub-valves 7, 7a, 7b open and close. Closing the main valves 6, 6a, 6b is illustrated by arrow C1, opening the main valves 6, 6a, 6b is illustrated by arrow O1, opening the sub-valves 7, 7a, 7b is shown by arrow O2, and closing the sub-valves 7, 7a, 7b is illustrated by arrow C2. The predetermined time period may be shorter than a continuous period including one or all of the operating positions of the valves 6, 6a, 6b, 7, 7a, 7b. For example, it can be from when the main valves 6, 6a, 6b close as illustrated by arrow C1 to when the sub-valves 7, 7a, 7b close as illustrated by arrow C2.

[0064] The two similar valves 6, 6a, 6b, 7, 7a, 7b never function in exactly the same way, and when setting up the fuel supply system 4 and the cylinders 2, 3, 14, 15, etc., changes will occur from one fuel supply passage 5, 5a, 5b to the other fuel supply passages 5, 5a, 5b. By measuring and comparing the pressures in the two equivalent passages 5, 5a, 5b, leaks in either the main valves 6, 6a, 6b or the auxiliary valves 7, 7a, 7b, or malfunctions in either the main valves 6, 6a, 6b or the auxiliary valves 7, 7a, 7b can be detected early. Changes in the pressure signals 9, 9a, 9b can be due to pressure changes caused by the internal combustion engine 1 or the settings of the valves 6, 6a, 6b, 7, 7a, 7b themselves. However, when the internal combustion engine 1 or the valves 6, 6a, 6b, 7, 7a, 7b operate as intended, the pressure signals 9, 9a, 9b for one fuel supply passage 5, 5a, 5b involving both the main valves 6, 6a, 6b and the auxiliary valves 7, 7a, 7b will change in the same pattern as those for the other fuel supply passages 5, 5a, 5b involving both the main valves 6, 6a, 6b and the auxiliary valves 7, 7a, 7b.

[0065] As described above, fuel is injected into the first cylinder 2 before being injected into the second cylinder 3, so the peaks of the first pressure signals 9, 9a are shifted in time relative to the peaks of the second pressure signals 9, 9b. Therefore, by measuring and comparing the pressures in the two equivalent passages 5, 5a, 5b, when one supply passage 5, 5a, 5b supplies fuel to the first cylinder 2 and the other supply passage 5, 5a, 5b supplies fuel to the second cylinder 3, the first pressure signals 9, 9a are shifted in time from the second pressure signals 9, 9b. When comparing these pressure signals 9, 9a, 9b, the first pressure signals 9, 9a are shifted in time to match the pattern / continuity of the second pressure signals 9, 9b so that the opening and closing of the valves 6, 6a, 6b, 7, 7a, 7b are aligned.

[0066] The comparison unit 10 can be a central processing unit (CPU), a control unit, a comparator unit, or a comparator based on hardware or software. The comparison unit 10 can use pattern recognition software.

[0067] The fuel supplied through the main supply passage 12 can be propane, ethene, ethane, butane, methanol, methane, ethanol, ammonia, propylene, butylene, isobutane, n-butane, hydrogen, kerosene, nitromethane, liquefied petroleum gas, bioethanol, or biodiesel. Thus, the fuel can be the only fuel supplied to cylinders 2, 3, 14, and 15, or can be a secondary fuel accompanied by a primary fuel that is diesel, gasoline, or oil. The fuel can be liquid or gaseous. Thus, the primary fuel can have a sulfur content of at least 0.05%.

[0068] The present invention also relates to a leak detection method for detecting leaks in valves 6, 6a, 6b, 7, 7a, 7b in a fuel supply system 4 for at least a first cylinder 2 and a second cylinder 3 of an internal combustion engine 1. In this method, first pressure signals 9, 9a are measured by first pressure sensors 8, 8a between a first main valve 6, 6a and a first sub-valve 7, 7a in first cylinder fuel supply passages 5, 5a of the fuel supply system 4 during a first time period, and second pressure signals 9, 9b are measured by second pressure sensors 8, 8b between a second main valve 6, 6b and a second sub-valve 7, 7b in second cylinder fuel supply passages 5, 5b of the fuel supply system 4 during the first time period or a second time period. The first pressure signals 9, 9a are compared with the second pressure signals 9, 9b to detect a leak in one of the valves 6, 6a, 6b, 7, 7a, 7b.

[0069] The present invention also relates to a computer program product comprising a computer-readable medium holding computer program code means which, when loaded, cause the computer program product to cause a computer to execute the leak detection method.

[0070] Although the present invention has been described above in connection with preferred embodiments of the present invention, it will be apparent to those skilled in the art that some modifications can be recognized without departing from the present invention as defined by the following claims.

Explanation of Signs

[0071] 1 Internal combustion engine 2 First cylinder 3 Second cylinder 4 Fuel supply system 5, 5a First cylinder fuel supply passage 5, 5b Second cylinder fuel supply passage 6, 6a First main valve 6, 6b Second main valve 7, 7a First sub-valve 7, 7b Second sub-valve 8, 8a First pressure sensor 8, 8b Second pressure sensor 9, 9a First pressure signal 9, 9b Second pressure signal 10 Comparison unit 11 Pump 12 Main supply passage 12a First part 12b Second part 14 Third cylinder 15 Fourth cylinder C1 Close main valves 6, 6a, 6b C2 Close sub-valves 7, 7a, 7b O1 Open main valves 6, 6a, 6b O2 Open sub-valves 7, 7a, 7b P1 First pattern P2 Second pattern

Claims

1. An internal combustion engine (1) for the propulsion of a ship, said internal combustion engine (1) having at least one cylinder (2), A fuel supply system (4), comprising: a first cylinder fuel supply passage (5, 5a) including a first main valve (6, 6a) and a first sub-valve (7, 7a) arranged upstream of the first main valve (6, 6a); a second cylinder fuel supply passage (5, 5b) including a second main valve (6, 6b) and a second auxiliary valve (7, 7b) arranged upstream of the second main valve (6, 6b); A fuel supply system (4), a first pressure sensor (8, 8a) providing a first pressure signal (9, 9a) is arranged between the first main valve (6, 6a) and the first sub-valve (7, 7a), and a second pressure sensor (8, 8b) providing a second pressure signal (9, 9b) is arranged between the second main valve (6, 6b) and the second sub-valve (7, 7b); The internal combustion engine (1) further comprises a comparison unit (10) for comparing the first pressure signal (9, 9a) with the second pressure signal (9, 9b) to detect a discrepancy between the first pressure signal (9, 9a) and the second pressure signal (9, 9b).

2. 2. The internal combustion engine (1) of claim 1, wherein the at least one cylinder is a first cylinder (2) and the internal combustion engine (1) further comprises a second cylinder (3).

3. 3. The internal combustion engine (1) of claim 2, wherein the first cylinder fuel supply passage (5, 5a) is in fluid communication with the first cylinder (2) and the second cylinder fuel supply passage (5, 5b) is in fluid communication with either the first cylinder (2) or the second cylinder (3).

4. 4. An internal combustion engine (1) according to any one of claims 1 to 3, wherein the fuel supply system (4) comprises a main supply passage (12) fluidly connected to the first cylinder fuel supply passage (5, 5a) and to the second cylinder fuel supply passage (5, 5b).

5. 5. An internal combustion engine (1) according to any one of claims 1 to 4, wherein the first pressure sensor (8, 8a) measures a real-time and / or continuous first pressure signal (9, 9a) and the second pressure sensor (8, 8b) measures a real-time and / or continuous second pressure signal (9, 9b).

6. 6. An internal combustion engine (1) according to any one of claims 1 to 5, wherein the fuel is propane, butane, methanol, methane, ethanol, ethane, ethene, ammonia, propylene, butylene, isobutane, n-butane, hydrogen, kerosene, nitromethane, liquefied petroleum gas, bioethanol or biodiesel.

7. 7. An internal combustion engine (1) according to any one of the preceding claims, wherein the main valve (6, 6a, 6b) has an opening time period that is shorter than an opening time period of the secondary valves (7, 7a, 7b).

8. 8. An internal combustion engine (1) according to any one of the preceding claims, wherein the auxiliary valves (7, 7a, 7b) open before the main valves (6, 6a, 6b) open.

9. 9. An internal combustion engine (1) according to any one of claims 1 to 8, wherein the first pressure signal (9, 9a) forms a first pattern (P1) and the second pressure signal (9, 9b) forms a second pattern (P2), and the comparison unit (10) compares the first pattern (P1) with the second pattern (P2) to detect a correlation and to verify whether the correlation is within a predetermined interval.

10. A leak detection method for detecting a leak in a valve (6, 6a, 6b, 7, 7a, 7b) in a fuel supply system (4) for supplying fuel to at least one cylinder (2) of an internal combustion engine (1) according to any one of claims 1 to 9, comprising: measuring the first pressure signal (9, 9a) by the first pressure sensor (8, 8a) between the first main valve (6, 6a) and the first sub-valve (7, 7a) in the first cylinder fuel supply passage (5, 5a) of the fuel supply system (4) during a first time period; measuring the second pressure signal (9, 9b) by the second pressure sensor (8, 8b) between the second main valve (6, 6b) and the second auxiliary valve (7, 7b) in the second cylinder fuel supply passage (5, 5b) of the fuel supply system (4) during the first time period or the second time period; comparing said first pressure signal (9, 9a) with said second pressure signal (9, 9b) to detect a leak in one of said valves (6, 6a, 6b, 7, 7a, 7b); 13. A method for leak detection comprising:

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